This invention relates to a shaft seal ring which has a sealing lip made of an elastic material. The air-side contacting surface of the sealing lip which is arranged at an inclination to the seal ring axis and thus to the shaft surface has a plurality of circumferentially distributed rib pairs. The individual ribs extend at an alternately opposite inclination to the circumferential direction and meet in the sealing edge.
Shaft seal rings having rib-like raised portions which are disposed at an inclination to the sealing edge and which serve for returning leakage liquid to the liquid side of the seal are generally known and are disclosed, for example, in French Pat. No. 1,227,078 to which corresponds British Pat. No. 888,198. By virtue of arranging the ribs -- which extend up to the sealing edge -- in a groupwise or individually alternating inclination with respect to the circumferential direction, there is sought to provide a return effect -- which is independent from the direction of shaft rotation -- for the leakage liquid that has escaped underneath the sealing edge. Further, in the German Laid-Open Application (Offenlegungsschrift) No. 2,021,382 there are disclosed ribs which are arranged in an alternately opposite inclination with respect to the circumferential direction which criss-cross one another and which extend from the sealing edge up to an axially spaced bounding edge of the air-side contact face. Between the ribs rhomboidal contact face zones are defined. Due to the relatively small angle of inclination (less than 20.degree.) between each individual rib, on the one hand, and the sealing edge, on the other hand, there is formed in the circumferential direction, a relatively wide contact face with the shaft surface at the location of the sealing edge where two ribs meet. In service, the magnitude of this contact face further increases due to wear and thus the risk of leakage in this zone from the liquid side towards the air of the shaft seal will be particularly significant. Ribs having relatively small angles of inclination with respect to the sealing edge are, furthermore, excessively long and thus it is not feasible to provide, with sufficient accuracy, the curved contact faces of the seal making dies with grooves that correspond to the shaft seal ribs. For this reason the ribs are arranged at a greater angle of inclination with respect to the sealing edge and, as a result, they can be relatively short, as may be seen in British Pat. No. 1,239,873.